05 silverado heat/ ac control

the heater/ac fan knob will not work on 5 it will work fine on 1 thru 4 but not 5. The manual said that if the blower doesn't work on 5 the the blower resistor is bad so i changed it. after about 1 min the fan quit working altogether, so i put the old resistor back in and it work all the way up to the 4th setting. Now the old resistor has gotten hot and melted the plastic on the high speed terminal does anybody think the heater/ac control switch is the cause.